Propeller-twisting press



June 12, 1928. 1,673,564

C. E. HAZTHORN ET AL PROPELLER TWI S TING PRES S Filed r 20 5Sheets-Sheet 1 lNws-N'roRs CHARLEfi E. HATHORN w YLVAHUS A. REED.

PROPELLER TWI S TI NG PRES 5 Filed April 20, 1926 3 Sheets-Sheet 5INVENTORJ. CHARLE5E HATHORN By finvAmusARzzo.

AT NEY Patented June 12, 1928.

UNITED STATES 1,673,564 PATENT OFFICE.

CHARLES E. HATI-IORN, OF HEMPSTEAD, AND SYLVANUS A. REED, OF NEW YORK,

N. Y., ASSIGNORS TO CURTISS AEROPLANE & MOTOR COMPANY, INC., A CORPORA-'I'ION OF NEVT YORK.

PROPELLER-TWISTING PRESS.

Application filed April 20, 1926.

Our invention relates to propellers and more particularly to the m ihodof and apparatus for twisting metal propellers of aircraft.

In the manufacture of metal propellers for aircraft the propeller blankis first milled to change its cross-section from rectangular toapproximately aerofoil form. This having been accomplished the propellerblank is ready to be twisted. Heretofore in twisting the propeller blanka rotary twisting machine has been used. Such a machine, whileespecially designed for twisting and bending the propeller blank, isnevertheless objectionable in that, due to the peculiarity of the twist,a multiple number of separate and wholly independent machine operationsare required to be performed. One blade of the propeller blank is firstclamped between the jaws of the twisting machine about 12 incl cs outfrom the transverse center line of the blank and given an initial twistof approximately 40 degrees. The propeller blank is then unclaniped,withdrawn from the machine, and reset exactly as before except that theopposite or untwisted propeller blade is clamped in place. Thus set,with said jaws engaging said opposite blade at a corresponding point outfrom said center line, said opposite blade is given an initial or centertwist exactly the same as its companion. This initial twist of eachblade is in each instance constant, that is to say, if a twist of 40degrees is given each blade at its 12-inch station out from said centerline, each said blade throughout the remaining portion of its lengthwill bear to the untwisted center portion of the blank a i0 degreeangle. Unfortunately, however, if properly shaped or twisted, the bladeangles of an aeronautical propeller vary. Generally speaking suchvariation ranges anywhere from approximately 40 degrees at the bladeroot to approximately 15 degrees at the tip. To obtain this graduallydiminishing blade angle a second series of machine operations isrequired. These operations, of which there are many, the numberdepending upon the particular propeller design, are usually performedwith the same machine as are the initial or center twist operations andare generally designated the reverse or countertwist operations. Eachblade, as it is reversely or counter-twisted, is acted upon re- SerialNo. 103,316.

peatedly and separately altho in each instance the repeated operationsare the same. At intervals from the innermost station outwardly eachblade is marked off at predetermined intermediate stations. Thesestations indicate the exact spot or point at which the blade should beheld between the jaws of the machine during each successive reverse orcounter-twist, and, as such stations are usually anywhere from sixinches to twelve inches apart, and asthe propeller blank must be clampedat every or at least every other station, and a certain degree ofreverse twist imparted to each blade after each successive clamping,obviously the operations incident to properly reversely twisting orcountertwisting the propeller blank are numerous. Again unfortunately,the blade angles obtained by thus reversely twisting the propeller blankare only approximately correct and must afterwards be checked andcorrected by other means necessitating additional work and the furtherhandling of the propeller blank. Moreover, after twisting the blank andcorrecting the blade angles, it is further important that the axis ofeach blade be canted or bent forward slightly to relieve, during actualuse of the propeller, certain bending stresses known at this time toexist. This latter bending operation is usually performed by hand.

An object of the present invention is to eliminate the many successiveand tedious operations above outlined by providing, instead of rotarytwisting machines, a propeller twisting press. Preferably such presscomprises co-acting dies, adjustable for different designs ofpropellers, between which the propeller blank is laid; means for holdingthe propeller blank in place between said dies; and additional means forbringing said dies together. In bringing said dies together (thruhydraulic or other power means), the propeller blank, in one and thesame operation, is initially twisted, reversely or counter-twisted, andbent longitudinally as aforesaid; the initial twist, the countertwist,and the longitudinal bend, in each instance, being so exact and soperfect as to wholly eliminate the heretofore subsequent check andcorrection accorded the angle of the propeller blades. By thusperforming, in a single operation, the functions heretofore performed bynumerous operations, the

manufacturing cost of metal aeronautical propellers is very appreciablyreduced.

A further object of the invention is to so form the co-acting dies ofthe propeller press as to subjectthe blank to the action of the dies atinter 'als or stations so relatively spaced as to produce in the blank asubstantially uniformly varying angle as d1st1n guished from the more orless successive pronounced angular variations produced heretofore.

A still further object of the invention 13 the provision of a novel termof holding means whereby the propeller blank is firmly held between thedies and against movement in any direction other than rotary orvertical. such rotary movement. at the ends of the blank, beingessential to the completion of the initial as well as the counter-twistoperations.

Other objects, advantages and characteri tics of the invention will behereinafter pointed out.

In the drawings, wherein like reference characters denote like orcorresponding parts,

Fig. 1 is a side elevation of the press;

Fig. 2 is a horizontal section on the line 22 of Fig. 1;

Fig. 3 is a side elevation of a portion of each die and its associatedplate showing the relation of the propeller blank thereto as the diesapproach one another in a twi t ing operation;

Fig. 4 is a plan view of the lower die showing the propeller blank readyto receive its various twists;

Fig. 5 is an end view of the die portion of the press showing the mannerin which the blank ends are clamped or held in place;

Fig. 6 is a similar view showing the relation of the press parts uponthe completion of the 'arious blank twists;

Fig. 7 is a section on the line 77 of Fig. 3;

Fig. 8 is a view similar to Fig. 7 with the dies brought together tocomplete the propeller twist;

Fig. 9 is a perspective view of one of the die pieces and die blocks;

Fig. 10 is a perspective view of a properly twisted propeller blank. thebroken line indicating the configuration of the blank prior to receivingthe twist, and

Fig. 11 is a view similar to Fig. 8 illustrating a modification.

In the embodiment of the invention selected for illustration. ahydraulic press of more or less conventional form is shown. Preferablysuch press comprises a ba e plate 20. a top plate 21, a ram (not shown)and such other ordinary hydraulic press parts as operating mechanism 22and supporting frame. the latter consisting of uprights a cross-head 2tand a base portion 25 within which the ram is enclosed. This particularform of hydraulic press, however, is merely illustrative, and aditl'erent l'orm ot press, other than hydraulic, it desired, may beused.

To each of the plates 20 and 21 of the press a die-carrier is l'astcncd.The diecarricr ill of the plate it! i mounted thereon and incross-:rction is ol approximately channel l'orm. lt is laterally bracedas at QT to said brace plate and at its opposite ends is provided withvertically extending guide arms The other of the die-carriers,designated as it). tastcned to and against; the underl'aee ot' the topplate 21. and like the die-carrier :30. it too i laterally braced. Thebracing $30 for the die-carrier 29, however. is carried. not to itssupporting plate, but directly to the cross-head 241 of the frame. Thisditlcrence in the bracing arrangement for the two plates 20 and 21 ismade possible by the fact that the plate 21 is fixed in its relation tothe supporting jl'rame whereas the plate 20 vertically movable.Otherwise the die-carriers 26 and 25) are the same. The guide arm 2s. otwhich there are four, two at each end of the die carrier :26. hear atall times directly against the vertical side walls of the fixeddie-carrier Q9.

Within the l'acin channels of the two diccarriers 26 and 2!) the.co-acting press dies are fastened. 3oth said dies, the lower designatedin its entirety as 31, and the upper similarly designated as 32. aresubstantially identical in size, form and construction. Each diecomprises a plurality of die-holding blocks 33 and a similar number ofdiepicccs or sections 3-}. These die-pieces 31 are preterably ofsemi-disc form and except; tor a slight ditl'erence in the configurationof the active ub'-'tantially straight edge 35 of each. 111" alsoidentical. The die-holding blocks 23 extend transversely of thediecarriers and are removably fastened within the channels thereof bybolts 36. The top face of each die-block 33 is hollowed out as at $37 toreceive in the recess thus formed, one of said die-pieces 3-}. aiddie-pieces fit snugly within said recesses and bear firmly throughout'their respective rounded edges directly against the similarly roundedbottom recess walls. Such bearing contact. plus the block side wallengagement, otlcrs suflicicnt; contact area between the die-pieces andthe die-blocks to hold the former against. both lateral and verticalrelative movement under all circumstances. Bolts 38 penetrating thedie-block ends and fitting bolt holes 39 formed in the die-pieces.firmly hold said die-pieces against rotational movement when properlyset. lly graduating the rounded edge of each die-piece in degrees asindicated atv 40, each said die-piece may be accurately separatelyadjusted as desired.

As previously explained, an aeronautical ltltl propeller, if properlyshaped, is required to be twisted in a manner such that the bladesthereof present to the right angle plane of its longitudinal axis adegree angle or thereabouts at the innermost blade stations which areusually twelve inches out from the transverse center line of thepropeller blank; such blade angle gradually lessening from said twelveinch station outwardly to approximately a fifteen degree angle at theblade tip. To obtain this peculiar gradually diminishing blade anglefrom said twelve inch station outwardly, the active edges of the severaldie-pieces 84: at opposite sides of the transverse center line of eachdie present, when viewed from the die ends, (see Fig. 7) slightlydifferent angles at each blade station, the angles increasing inwardlytoward the die centers in a like manner and to the same extent from theoppositeouter ends of said dies. As the diminishing blade angle ispreferably more pronounced in the vicinity of the points at which amaximum twist is desired, the diepieces, at the inner blade stations areplaced closer together than they are at the outer blade ends.

In Fig. 10 of the drawings the propeller blank is illustrated in brokenlines as it appears before being pressed or twisted and in full lines itis illustrated as it appears properly shaped. Such blank is designatedas 41 and the center opening formed therein is designated as 42. Thiscenter opening a2 is formed in the blank at the inter-section of thelongitudinal and transverse center lines thereof before said blank istwisted and shaped. lVith said opening 42 properly located the propellerblank is laid between the dies 31 and of the press. To center the blankrelatively to said dies a spindle 43 is provided. Said spindle projectsvertically upwardly from the exact center of the lower die 31 and isadapted to snugly engage in said center opening 4-2 of the propellerblank. By providing a comparatively snug fit between said spindle andsaid center opening the propeller blank is firmly held againstrotational and lateral movement in the vicinity of its transverse centerline, against longitudinal displacement under all circumstances, and ina manner such that, during the twisting operation, other than acorresponding twist at opposite sides of said center line cannotpossibly occur.

As a further means for holding the propeller blank during a twistingoperation, end clamps or devices are provided. These end clamps aremounted between vertical guide rails 44 (two for each clamp) fastened tothe die-carrier 26 at its opposite ends. Each clamp comprises a fixedjaw a5. a movable jaw 46, clamp ends or head portions 4:7, and clampingbolts 48. The head portions 47 (see Figs. 5 and 6) of each clamp arepreferably formed integrally with the fixed jaw 45 thereof and areadapted to bear on and fit between the guide rails at as indicated. Saidhead portions t? are also provided with arcuate end grooves 49 withinwhich said guide rails al engage. In this manner said end clamps areheld against transverse or endwise movement the movable freely bothvertically and rotationally. A mark 50 on each clamp indicates the exactlongitudinal center line of the co-acting dies of the press.

In operation, a propeller blank is laid longitudinally of and betweenthe (Jo-acting dies 31 and 32 of the press with the spindle 43 extendingvertically thru the center hole 42 of the propeller blank. The ends ofthe propeller are then clamped between the aws 4.5 and 46 of the endclamps with the markings 50 on said clamps in registry with thelongitudinal center line of the propeller blank. Thus positioned andsecurely clamped between the press dies the blank 41 is ready to betwisted or shaped. As the dies 31 and 32 are brought together theinnermost die pieces 3st at opposite sides of the transverse center lineof the blank first bear thereon to positively twist it as said diesappreach each other. This first twist, due to the high angle of the diepieces at said inner most blade stations, constitutes what hasheretofore been designated the initial or center twist and it, theinitial or center twist, continues uninterruptedly until the desiredblade angle at said innermost blade stations is obtained. The reverse orcounter-twist operation, as intimated, is obtained while and during theinitial twist operation. the commencing only after such initial twistoperation is under way. The counter-twist operation, however, iscompleted at the same moment as said initial twist operation and due tothe varying angles of the outer die pieces is *ariable throughout therespective blade lengths. To longitudinally bend or cant the propellerblank shim 51 of different thickness may be inserted beneath the outerdie blocks as illustrated. No re-check or correction is required it andwhen the die-pieces are properly set. All bonds or twists are obtainedby the one operation, i. e., the bringing of the dies 31 and 32together.

In the modification of Fig. 11, instead of providing adjustabledie-pieces, die pieces 52 of a given configuration are provided. Suchdie-pieces are fastened between the die-car rier of the press by bolts53 and are preferably interchangcaible. For shaping or twistingpropeller blanks of different design, where non-atljustable die-piecesar used, a different set of such die-pieces must be provided for eachdesign that is different.

lVhile we have described our invention in detail in its presentpreferred embodiment, it will be obvious to those skilled in the artafter understanding our invention, that various changes andmodifications may be made. therein without departing from the spirit. orscope thereof. '0 aim in the appended claims to cover all suchmodifications and changes.

\Vhatwe claim is:

1. A press for twisting propellers including dies between which thepropeller is laid. rotatable clamps for holding said propeller in placebetween said dies, and means for bringing said dies together.

2. A press for twisting propellers including dies between which thepropeller is laid, guidestmounted at the die ends. clamps carried by androtatable within said guides for holding the propeller in place betweensaid dies, and means for bringing said dies together.

A press {or twisting propellers including dies between which thepropeller is laid, freely rotatable clamps mounted at the die ends tohold said propeller in place between said dies, means for holding eachsaid clamp against morementtransversely of said dies, and means forbringing said dies together.

4. A press for twisting propellers including dies between which thepropeller is laid, each die comprising a plurality of separatelyadjustable die-pieces, means for holding each die-piece in its adjustedposition, a center spindle for holding the propeller in place betweensaid dies, relatively movable end clamps likewise engageable with saidpropeller to hold it. in place between said dies, and means for bringingsaid dies together with the propeller held therebetween.

The method of twisting metal aeronautical propellers which consists inprogressively bringing to bear on the opposite faces of the propellerblank at dilterent star tions throughout its length a plurality ofindividually termed die-pieces each haying an engaging surface set at anangle cal culated to produce in a. finished product that particulartwist deemed correct for that particular station at which said die-piecebears.

(1. A press for twisting propellers comprising dies between which thepropeller is laid, each die including a. plurality of transverselyextending die pieces adapted to he indiridually adjusted to presenttoward the propellcr a working face. the angularit of which may bevaried by such adjustment, means for holding said propeller in placebetween said dies and means for bringing said dies together.

7. A. press for twisting propellers comprising dies between which thepropeller is laid, each die including a plurality of transverselyextending die pieces individualtv rotatable about an axis extendinglongitudinally of said die to \"ary the angle of the working 'l'acethereof. means for holding said propeller in place between said dies andmeans for bringing said dies together.

8. A press for twisting propellers comprising dies between which thepropeller is laid. each die including a plurality of freely removabletransversely extending die pieces adapted to separately engage, eachwithin a recess -formed within said (lie, means for holding saidpropeller in place between said dies and means for bringing said diestogether.

9. A press for twisting propellers comprising dies between which thepropeller is. laid. clamps for said propeller rotatable during thtwisting thereof. and means for bringing said dies together with thepropeller held in place by said clamps.

Tn testimony whereof we hereunto aflix our signatures.

CHARLES E. I*I. \'II-TORN. SYLVANUS A. REED.

